A fluid ejection system, for example, an ink jet printer, typically includes an ink path from an ink supply to a printhead that includes nozzles from which ink drops are ejected. Ink is just one example of a fluid that can be ejected from a jet printer. Ink drop ejection can be controlled by pressurizing ink in the ink path with an actuator, for example, a piezoelectric deflector, a thermal bubble jet generator, or an electrostatically deflected element. A typical printhead has a line or an array of nozzles with a corresponding array of ink paths and associated actuators, and drop ejection from each nozzle can be independently controlled. In a so-called “drop-on-demand” printhead, each actuator is fired to selectively eject a drop at a specific location on a medium. The printhead and the medium can be moving relative one another during a printing operation.
Ink is provided to a printhead from a source that can be internal or external to the fluid ejection system. The longer the flow path from the ink source to the printhead and the greater the number of connections required along the path, the greater chance of air bubbles becoming entrapped in the ink. Air bubbles can have a detrimental effect on printing quality from the printhead. Air bubbles can become entrapped during a filling operation or during a printing operation through leaks along the length of the flow path.